Robot gripper assemblies which include arms that carry workpiece-receiving devices are known in the art. Federal Republic of Germany Patent No. 3,517,460 discloses V-shaped receiving devices which are oriented toward each other to enable the moving of round parts. For gripping on or under other similar parts the configurations of the receiving devices could be specially adapted to correspond to the particular part or workpiece shapes. With the increasing use of industrial robots has come an attendant demand for receiving devices which will also accommodate workpieces of irregular surface shapes; such irregular shapes are particularly difficult to grasp by heretofore known industrial robots.